Centauri Dreams has written before about Grover Swartzlander (University of Arizona), who is developing new ways to screen out the light of a star to make it possible for astronomers to study the planets around it. At the heart of Swartzlander's effort is something called an optical vortex mask, which is said to be 'a thin, tiny, transparent glass chip that is etched with a series of steps in a pattern similar to a spiral staircase.' And here's how this chip does its job: incoming light slows down more in the thicker parts of the chip than in the thinner ones, with the result that some waves of light eventually becomes 180 degrees out of phase with others. Reaching the 'eye' of the vortex, the waves that are 180 degrees out of phase with one another cancel each other out, so that a dark central core remains. Swartzlander says the effect is like light following the threads of a bolt; the distance between adjacent threads is crucial to the outcome. So could this technology be used to...

An interesting specialty in exoplanetary science is the simulation of planetary orbits. It's intriguing, for example, to place a hypothetical terrestrial planet into a system with known giant planets to see what happens. After all, we know that many exoplanetary systems contain potentially stable orbits for such planets; in fact, one-fourth of known systems can support a planet in their habitable zone. And while we don't know yet whether such worlds exist, we can draw useful conclusions from modeling their orbits if they are there. Such are the premises of a new paper by Sean Raymond (University of Washington, Seattle) and Rory Barnes (Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder). The two simulate terrestrial planets in four systems: 55 Cancri, HD 38529, HD 37124, and HD 74156. And here is a key issue: most planets we've found so far are 'hot Jupiters,' in tight, close orbits around their primary. For a terrestrial planet to co-exist with such...

Centauri Dreams recently discussed the planets around HD 73526, as described in detail on astronomer Gregory Laughlin's Systemic site. HD 73526c seemed attractive as a venue for life-bearing moons -- a gas giant, it orbits well within its parent star's habitable zone. The post inspired questions from readers on whether the chances for life on any large moons of such a planet would be minimized by Jupiter-style radiation fields. And given the unusual orbital resonance between the two planets, questions also arose about how these gas giants might have formed. Laughlin (University of California, Santa Cruz) was kind enough to answer these queries. His responses follow, with my inserted comments in italics. The radiation environments around both HD 73526 b and c are probably more intense than in the vicinity of Jupiter. This increase would mainly be the result of the planets having larger masses than Jupiter, which gives them more vigorous interior convection and hence stronger magnetic...

HD 73526 is a G6 star (i.e., a solar-like main sequence dwarf) that has just made some interesting news. As Greg Laughlin writes in a new posting on his Systemic site, Paul Butler, Geoff Marcy, Chris Tinney and collaborators with the Anglo-Australian Planet Search Project have found that the planetary system around the star displays an unusual resonance whose motion over time can be viewed in this online mpeg file. But even more striking is the nature of the two gas giant planets found here. The inner (HD 73526b) orbits with a 188 day period, while the outer has a period of 379 days. Let Laughlin tell it: Planet c is a true room temperature gas giant. Liquid water likely blows in gusty sheets across its cloudy skies. (And it's worth noting that any large moons circling HD 73526 c lie pleasantly within the stellar habitable zone.) Got that? Centauri Dreams yields to no one when it comes to fascination over exoplanetary orbits, particularly unusual resonances between distant worlds,...

The budgetary demise of Terrestrial Planet Finder has cast a pall over some researchers, but it may have energized an entirely different solution. What if I told you that in the 2013-2015 time frame we may get conclusive images that tell us whether or not there are terrestrial worlds around Tau Ceti, Epsilon Eridani, and Centauri A and B? Images that allow us to examine the habitable zones of as many as 100 stars over a three-year period? With TPF gone, the idea sounds like a fantasy, but my recent conversation with astronomer Webster Cash revealed it to be anything but. Cash (University of Colorado at Boulder) has been involved in the development of a concept most recently called New Worlds Imager, one that began as an enormous 'pinhole camera' design, as I discussed in Centauri Dreams (the book) in 2004. Within the last 18 months, the design has morphed into a low-cost mission using an occulter (call it a 'starshade') to mask the light of the star being observed so as to reveal...

Margaret Turnbull (Carnegie Institution of Washington) has a job Centauri Dreams can't help but envy. The astronomer is a specialist in identifying stars that have habitable zones -- stars, in other words, where life is possible. Back in 2003, Turnbull and colleagues published a list of 17,129 such stars, based on factors such as age (how long does it take life to develop?), stellar mass (larger stars may not live long enough to produce productive habitable zones) and metallicity (a measure of the heavy metals needed for planetary formation). Narrowing a galaxy of between one and two hundred billion stars down to 17,129 candidates is no small feat, but Turnbull has now gone one better, choosing the top five candidate stars for those engaged in SETI, the search for extraterrestrial intelligence. That list involves choosing stars where technological civilizations are most likely to have developed, but Turnbull complements it with a second list of six stars likely to have Earth-like...